K3Nb3B2O12 single crystal

K3Nb3B2O12 single crystals are of great interest as materials with unique combination of ferroelectric, ferroelastic and superionic properties. These properties are determined by peculiarities of their atomic structure consisting of rigid framework from NbO6 octahedra and plane BO3 groups with wide channels occupied by labile K ions.

The K3Nb3B2O12 single crystals and their solid solutions with a various degree of substitutions K+ by Na+ or Rb+, Nb5+ by Ta5+ or Sb5+, and B3+ by Si4+ are grown and their phase transitions and physical properties are investigated.

It is shown that the above crystals undergo to 7 phase transitions (the temperature is indicated in oC for the pure K3Nb3B2O12):


which are accompanied by intensive anomalies of dielectric permeability e33 and by changes in domain structure. The high temperature phase a is hexagonal one with the point group -62m, phase b has symmetry 3m or -62m, other low-temperature phases are monoclinic or triclinic. The b « a phase transition is anti- or ferroelectric, whereas other transitions have mixed ferroelectric-ferroelastic nature.

K3Nb3B2O12 and solid solutions demonstrate superionic properties and high conductivity caused by high mobility of K+ cations. Electric conductivity s33 of pure K3Nb3B2O12 crystals is near to 10-5 Ohm-1cm-1 at 300oC with a sharp drop at d « g transition by an order of magnitude.

     The full substitutions of B by Si is possible and K3Nb3Si2O13 single crystals are grown and studied. They have hexagonal growth form but at the room temperature have lower symmetry and are divided into domains. These crystals are characterized by high dielectric permeability e33 which is about 4000 at room temperature and rises with temperature.

Domain structure of K3Nb3B2O12 single crystal at room temperature under polarized light


Main publications:
  1. V. I. Voronkova, V. K. Yanovskii, I. N. Leont’eva, N. I. Sorokina, V. I. Simonov. Growth, Structure, Polymorphism, and Physical Properties of KNbB2O6 and K3Nb3B2O12 Crystals // Crystallography Reports. 1996. V. 41. No. 5. P. 837 - 840.

  2. E.P. Haritonova, V.I. Voronkova, V.K. Yanovskii, S.Yu. Stefanovich, A.V. Mosunov. Phase transitions and domain structure of ferroelectric-ferroelastic-superionic crystals K3Nb3B2O12 and their solid solutions. // Ferroelectrics. 1999. V. 221. p. 73 - 77.

  3. T.Yu. Losevskaya, E.P. Kharitonova, V.I. Voronkova, V.K. Yanovskii, S.Yu. Stefanovich, N.I. Sorokina, V.I. Simonov. Superionic transitions in the K1-xTi1-xNbxOPO4 and K3Nb3B2O12 crystals. // Crystallography Reports. 1999. V. 44. No 1. p. 95 - 97.

  4. V.I. Voronkova, E.P. Kharitonova, V.K. Yanovskii, S.Yu. Stefanovich, A.V. Mosunov, N.I. Sorokina. Growth, structure and properties of ferroelectric-ferroelastic-superionic K3Nb3B2O12 and K3-xNaxNb3B2O12 crystals. // Crystallography Reports. 2000. V. 45. No 5. p. 816 - 820.

  5. E.P.Kharitonova, V.I.Voronkova, V.K.Yanovskii, and S.Yu.Stefanovich. Polymorphism of ferroelectric, ferroelastic, superionic crystals K3Nb3B2O12 and K3-xNaxNb3B2O12. // Inorganic Materials. 2002. V.38. No.8. p.819 - 824.

  6. E.P. Kharitonova, V.I. Voronkova, V.K. Yanovskii. Phase transitions and ferroelectric and superionic properties of K3Nb3B2O12 - K3Nb3Si2O13 single crystals. // Inorganic Materials. 2003. V. 39. No. 2. p. 127 - 132.

  7. E.P. Kharitonova, V.I. Voronkova, V.K. Yanovskii. Phase transitions and physical properties of K3Nb3B2O12 and K3Nb3-xMxB2O12 (M = Ta, Sb) crystals. // Inorganic Materials. 2003. V.39. No.6. p.710 - 715.



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